1. Field of the Invention
The invention relates to a printed dipole antenna useful as a radiating element in microwave and millimeter wave arrays, and more particularly to a printed antenna with an integral balun and 180.degree. phase shift bit useful in arrays which are electronically steered, and/or operated in the monopulse mode.
2. Prior Art
The present invention represents an extension of the invention of B. J. Edward and D. E. Rees, U.S. patent application Ser. No. 935,030, filed Nov. 26, 1986, entitled A MICROSTRIP FED PRINTED DIPOLE WITH AN INTEGRAL BALUN.
Electronically scanned phased arrays employ multi-bit phase shifters to steer a beam over a desired angular range. In fully electronically steered arrays the beam may be repositioned electronically in both elevation and azimuth by altering the relative phases of the antenna's radiating elements. This requires each element to have a multi-bit phase shifter whose state may be selected independently from all others. The conventional 180.degree. phase shift bit exhibits both design complications and a relatively high insertion loss.
An array may be electronically steered in one plane and mechanically steered in the other to drastically reduce the number of individual phase shifters. This usually produces a cost saving at the expense of steering flexibility but is a common compromise in modern Solid State radars. Since the beam azimuth position is a function of the mechanical rotation of a usually large and cumbersome array, such a mechanically steered radar has less flexibility than an electronically steered array in the azimuth search rate or target dwell times.
Reductions in cost, design simplifcations, or performance improvements in the means for achieving electronic steering tend to further facilitate the more wide spread application of electronic steering.
Radars have a need to invert the phase of all the elements on one-half of the array in the process of forming a difference beam to refine the accuracy of an angular reading. Customarily, the phase is inverted from a feed assembly. The present arrangement provides a design alternative for achieving difference beam formation, and does so without substantial added complexity.